Seat belt web stop apparatus and method

ABSTRACT

A web stop button may utilize plastic deflection to provide more secure and reliable attachment to a seat belt. The web stop button may have a first button member and a second button member. The first and second button members may each have multiple pieces attached together via crimping or the like. Protrusions extend from the first button member and plastically deflect within the second member in response to force urging the first and second members together. The protrusions may be capable of piercing the seat belt strap and/or a portion of the second button member. Plastic caps may be used on one or both of the button members to provide a larger web stop button and enhanced trim color matching capability. The second button member is shaped to induce the plastic deflection, and may therefore have a simple domed shape or a more complex, generally toroidal domed shape.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to systems and methods for protecting vehicle occupants from injury. More specifically, the present invention relates to a novel web stop button and related methods that enhance the reliability and cost-effectiveness of seat belts.

[0003] 2. Description of Related Art

[0004] Seat belts have been instrumental in saving many thousands of lives in automobile accidents. Statistics consistently attest to the effectiveness of seat belts in reducing occupant injury. Seat belts are typically attached to automobile seats or to the interior of the automobile, adjacent to the seat. The invention of the three point safety harness, i.e., a lap belt used in conjunction with a shoulder harness, enhanced the life-saving effect of automotive seat belts.

[0005] Typically, three point safety harnesses have a retractor positioned at one end of the belt to take up slack in the belt. A latch plate is slidably coupled to the belt so that a user may grasp the latch plate and insert it into a buckle to simultaneously fasten the lap belt and the shoulder harness. When not in use, the belt typically hangs in a generally vertical orientation. A web stop button is attached to the belt so that, when the belt is not in use, the latch plate rests at a position conveniently reached by the vehicle occupant. In many seat belt types, web stop buttons may also limit the amount of the seat belt that can be taken up by the retractor, thereby preventing the seat belt from binding within the retractor.

[0006] Unfortunately, a number of problems exist with known web stop buttons. Many known web stop buttons are constructed of plastic, and are therefore subject to breakage. Web stop buttons typically have two parts that are attached together on opposite sides of the seat belt. Plastic materials are generally unable to sustain long-term plastic deflection; hence, the methods used to attach the two parts together typically utilize less sturdy forms of attachment such as snap fitting. Snap fit parts, whether constructed of plastic or other materials, may unfortunately be separable under stress. Some known web stop buttons even require alignment with a hole pre-formed in the strap prior to attachment. Thus, the cost and complexity of the button attachment process is increased.

[0007] Breakage and/or separation of known web stop buttons has been a major cause of warranty repair expenditures for automakers. Often, failure of the web stop button not only necessitates replacement of the button. Rather, in the absence of the button, the seat belt strap may become lodged in the retractor, thereby requiring repair and/or replacement of the retractor and strap. Hence, web stop button failure can cause considerable expense.

SUMMARY OF THE INVENTION

[0008] The apparatus and method of the present invention have been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by current seat belt web stop buttons. Thus, the present invention discloses web stop buttons and related methods that provide inexpensive, secure, and reliable attachment and web stop functionality.

[0009] To achieve the foregoing, and in accordance with the invention as embodied and broadly described herein in the preferred embodiment, an enhanced seat belt is provided. In one configuration, the seat belt includes a retractor disposed near an upper portion of a backrest of an automobile seat. A strap extends from the retractor, which is designed to take up slack in the strap, and to lock the belt against withdrawal from the retractor in the event of a collision. The strap has a first end disposed proximate the retractor, a second end attached to the vehicle via an anchor, and an intermediate portion between the first and second ends. The strap has a first side and a second side opposite to the first side.

[0010] A latch plate slidably engages the strap, and is designed to be removably anchored by a buckle assembly. A web stop button is attached to the seat belt to limit motion of the latch plate along the strap. An occupant of the seat may attach the latch plate to the buckle assembly to buckle themselves in the seat. The seat belt, in this configuration, acts as a three-point safety harness. Other seat belt types may alternatively be used with the web stop apparatus and method of the present invention.

[0011] The web stop button has a first button member and a second button member. The first and second button members are constructed generally of a metal such as brass. The first and second button members are attached together through the strap in such a manner that the first button member is disposed adjacent to the first side of the strap and the second button member is disposed adjacent to the second side of the strap. The first button member has a backing piece and a protrusion piece retained and partially covered by the backing piece. The second button member has a dome piece and a capture piece retained and partially covered by the dome piece.

[0012] The protrusion piece has a first protrusion and a second protrusion, which may be configured as first and second sharp prongs. Each of the prongs has a tip with a comparatively sharp point. The first and second sharp prongs extend through first and second openings formed in the strap. The first and second openings may simply be formed by pressing the first and second sharp prongs against the strap to pierce the strap. Thus, separate piercing or punching operations are not required to form the openings in the strap to receive the sharp prongs. The capture piece has an annular trough sized such that both of the sharp prongs may simultaneously impinge upon the annular trough after they have passed through the first and second openings in the strap.

[0013] The backing piece of the first button member has an outer wall with an interior surface, against which the protrusion piece rests. The backing piece also has a retaining lip that is crimped or otherwise shaped to hold the protrusion piece against the interior surface. The retaining lip defines an aperture in the backing piece, through which the protrusion piece is partially exposed. The protrusion piece has a disc disposed within the backing piece, with a periphery in contact with the retaining lip. The first and second sharp prongs extend from the disc and through the aperture.

[0014] The dome piece has a domed outer wall that defines an enclosure in the form of a domed chamber in conjunction with the capture piece. The dome piece has a domed interior surface with a generally concave shape. The dome piece also has a retaining lip shaped to hold the capture piece against the curvature of the domed interior surface. The retaining lip forms an aperture through which the capture piece is partially exposed. The capture piece has a curled edge shaped to lie within the outer edge of the domed interior surface and the retaining lip to permit secure retention of the capture piece within the dome piece. The capture piece has a central portion encircled by the annular trough.

[0015] In order to attach the first and second button members together, the first and second button members are first aligned on opposite sides of the strap. The first and second button members may be seated in opposing dies or other fixtures of a specialized press, and may be urged against each other by the press. The sharp prongs pierce the strap to form the first and second openings in the strap.

[0016] Upon impingement of the sharp prongs against the annular trough, first and second openings are formed in the annular trough as the first and second sharp prongs pierce and pass through the annular trough. The first and second sharp prongs thus enter the domed chamber. When the tips of the sharp prongs contact the domed interior surface, they are urged by the dome shape to move generally inward, toward each other. The sharp prongs fold generally parallel to each other in response to continued pressure urging the first and second button members together. The folding constitutes plastic deformation of the sharp prongs. In their folded state, the capture member interferes with removal of the sharp prongs from the domed chamber. Thus, the first and second button members are attached together in a comparatively secure and durable manner.

[0017] According to one alternative embodiment of the invention, first and second button members may similarly be used to form a web stop button. As in the previous embodiment, the first button member has a backing piece and a protrusion piece. The second button member has a dome piece and a capture piece. The protrusion piece and the capture piece may be identical to those of the previous embodiment. The backing piece and the dome piece are shaped somewhat differently from those of the previous embodiment, but are essentially the same in operation.

[0018] A first plastic cap is attached to the first button member, and a second plastic cap is attached to cover the second button member. The first plastic cap has a receiving chamber sized to receive the backing piece of the first button member. The first plastic cap also has a retention lip, which may be formed by heat staking or the like, which retains the backing piece within the receiving chamber. The retention lip defines an aperture through which a portion of the first button member is exposed. The first plastic cap also has a peripheral lip that extends toward the strap. The first plastic cap may have a central indentation for purposes of identifying the first plastic cap, displaying a trademark, or the like.

[0019] The second plastic cap has a receiving chamber sized to receive the dome piece. A retention lip is formed by heat staking or some other process to capture the dome piece within the receiving chamber. The retention lip defines an aperture through which a portion of the second button member is exposed. The second plastic cap has a peripheral lip that extends toward the strap.

[0020] The first and second plastic caps may be injection molded, stamped, or otherwise formed to shape. The first and second button members may then be inserted into their corresponding receiving chambers, and the first and second plastic caps may be processed to form the retention lips, thereby keeping the first and second button members in place within the first and second plastic caps.

[0021] The first and second plastic caps enlarge the effective size of the web stop button. Thus, the web stop button may provide a more effective barrier to undesired motion of the latch plate or to excessive take-up of the strap by the retractor. The first and second plastic caps may also be easily colored to match the interior trim of the vehicle. If desired, only the first plastic cap or only the second plastic cap may be used.

[0022] According to another alternative embodiment, a web stop button again has a first button member and a second button member. The first and second button members are each constructed substantially of a metal such as brass. Each of the button members has only a single unitary piece. The first button member has first, second, and third protrusions, or sharp prongs, arranged in radially symmetrical fashion around an axis of symmetry of the first button member. Each of the sharp prongs has a pointed tip. The strap has three corresponding openings, which may be formed by piercing the strap with the sharp prongs of the first button member.

[0023] The first button member has an outer wall and a contact lip that extends toward the strap. The contact lip may rest against the strap. The second button member has a domed outer wall that defines a domed chamber. The domed outer wall has a domed interior surface. However, the domed interior surface is not simply concave, but has a revolved circular shape characteristic of a portion of a torus. The second button member also has a contact lip that contacts the strap. The second button member further has an aperture disposed to receive the sharp prongs. A retention wall extends from the contact lip to the aperture.

[0024] As with the previous embodiments, the first and second button members are first aligned with each other on opposite sides of the strap. The first and second button members are urged together. The first, second, and third sharp prongs of the first button member form the first, second, and third openings in the strap. The sharp prongs need not pierce any part of the second button member, but rather simply enter the domed chamber through the aperture. The sharp prongs contact the domed interior wall and are forced to bend outward by the curvature of the domed interior surface. The sharp prongs generally fold outward such that the retention wall interferes with withdrawal of the sharp prongs from the domed chamber.

[0025] Through the use of plastic deflection, the web stop buttons described above enhance the reliability and durability of seat belts by reducing the incidence of web stop button failure. The web stop buttons are inexpensive and easy to install. No separate steps are required to form openings in a strap to permit attachment of the buttons. Through the use of plastic caps, the interior trim of the vehicle may relatively easily be matched without compromising the durability of the web stop button. These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order that the manner in which the above-recited and other features and advantages of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0027]FIG. 1 is a perspective view of a seat incorporating a seat belt according to one embodiment of the invention, with the seat belt in the buckled configuration to provide occupant protection;

[0028]FIG. 2 is an exploded, perspective view of the web stop button and a portion of the strap of the seat belt of FIG. 1;

[0029]FIG. 3 is a side elevation, section view of the web stop button and a portion of the strap of the seat belt of FIG. 1, in a fully assembled state;

[0030]FIG. 4 is a side elevation, section view of a web stop button and a portion of a strap of a seat belt according to one alternative embodiment of the invention; and

[0031]FIG. 5 is a side elevation, section view of a web stop button and a portion of a strap of a seat belt according to another alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The presently preferred embodiments of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus, system, and method of the present invention, as represented in FIGS. 1 through 5, is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention.

[0033] Through the use of plastic deflection, the present invention provides for easy and secure installation of web stop buttons for seat belts. Plastic deflection refers to permanent deflection of a material by application of a force. By contrast, elastic deflection is deflection that is not extensive enough to remain, but rather permits the material to return to a substantially undeflected state after the force is removed. The manner in which the above described principles are implemented by the present invention will be described in greater detail as follows.

[0034] For this application, the phrases “connected to,” “coupled to,” and “in communication with” refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, and thermal interaction. The phrase “attached to” refers to a form of mechanical coupling that restricts relative translation or rotation between the attached objects. The phrases “pivotally attached to” and “slidably attached to” refer to forms of mechanical coupling that permit relative rotation or relative translation, respectively, while restricting other relative motion.

[0035] The phrase “attached directly to” refers to a form of attachment by which the attached items are either in direct contact, or are only separated by a single fastener, adhesive, or other attachment mechanism. The term “abutting” refers to items that are in direct physical contact with each other, although the items may not be attached together. The terms “integrally formed” refer to a body that is manufactured unitarily, i.e., as a single piece, without requiring the assembly of multiple pieces. Multiple parts may be integrally formed with each other if they are formed from a single workpiece.

[0036] Referring to FIG. 1, a perspective view illustrates one embodiment of a seat belt 10 according to the invention. In FIG. 1, the seat belt 10 is in the anchored and buckled configuration. The seat belt 10 is shown coupled to a seat 12, which is a bench style seat, with the seat belt 10 positioned to protect an occupant of the central portion of the seat 12. The seat 12 is merely an example; a seat belt according to the invention may be used with any type of seat. As shown, the seat 12 has a bottom cushion 14 and a backrest 16. The backrest 16 has a lower portion 18 and an upper portion 20. A rearward surface is positioned behind the seat 12.

[0037] The seat belt 10 has a take-up mechanism, which may take the form of a retractor 30, disposed proximate the upper portion 20 of the backrest 16. As shown, the retractor 30 may be positioned on the rearward surface 22. In the alternative, the retractor 30 may be attached to a variety of other locations, such as the upper portion 20, the interior of the vehicle, or to a belt or stiff extension attached to the vehicle interior.

[0038] A strap 32 extends from the retractor 30 downward along the backrest 16. The retractor 30 preferably comprises a spring or some other resilient mechanism that enables the retractor 30 to take up slack in the strap 32. The retractor 30 may also be configured to lock the strap 32 against withdrawal from the retractor 30 in the event of a collision. The retractor 30 may be configured in a manner similar to that of known retractors for seat belts.

[0039] The strap 32 has a first end 33 attached to the retractor 30 and a second end 34 furthest from the retractor 30. The strap 32 also has an intermediate portion 36 between the first and second ends 33, 34. Furthermore, the strap 32 has a first side 38 and a second side 39 disposed opposite the first side 38. A latch plate 40 slidably engages the strap 32 and is normally disposed proximate the intermediate portion 36.

[0040] The second end 34 is coupled to the seat 12 via an anchor 42 disposed within the bite of the seat 12, i.e., at the junction between the bottom cushion 14 and the lower portion 18 of the backrest 16. The anchor 42 may be affixed within the bite via a pin (not shown) or the like. According to alternative embodiments, an anchor may be disposed beside or behind the seat. The positions of the retractor 30 and the anchor 42 may also be reversed, if desired.

[0041] The seat belt 10 may be latched by retaining the latch plate 40 with a buckle assembly 48. The buckle assembly 48 includes a buckle 49 designed to receive the latch plate 40. The buckle 49 is attached to the bite of the seat 12 via an anchoring belt 50. The buckle 49 includes a housing 52 with a button 54 that is accessible to an occupant of the seat 12. The buckle 49 may be configured in a manner similar to that of known seat belt buckles. As illustrated in FIG. 1, the seat belt 10 is in the buckled configuration. The occupant can release the seat belt 10 by pressing the button 54 of the buckle 49.

[0042] A web stop button, or button 56, is attached to the strap 32. The material used to form the strap 32 is often called “webbing.” Hence, the term “web stop button” is used. The button 56 prevents the latch plate 40 from sliding too far toward the anchor 42 when the seat belt 10 is not latched. Thus, the button 56 keeps the latch plate 40 within relatively easy reach of the occupant of the seat 12. As mentioned previously, a web stop button may also help control the length of the strap that is able to be taken up by a retractor to help avoid binding within the retractor. The configuration of the button 56 will be shown and described in greater detail in connection with FIG. 2, as follows.

[0043] Referring to FIG. 2, an exploded, perspective view illustrates the web stop button 56 of FIG. 1, together with part of the intermediate portion 36 of the strap 32. The button 56 has a longitudinal direction 60, a lateral direction 62, and a transverse direction 64. As shown, the button 56 includes a first button member 66 and a second button member 68.

[0044] The first and second button members 66, 68 may each be constructed substantially of a metal such as brass. Alternatively, other materials, including plastics, ceramics, elastomers, composite materials, or other metals may be used. Other exemplary metals include copper, aluminum, and steel. If desired, the web stop button 56 may be of a type available from YKK Universal Fasteners, Inc. In addition or in the alternative, the configuration of the web stop button 56 may be as follows.

[0045] The first and second button members 66, 68 may each include multiple pieces. For example, the first button member 66 includes a backing piece 70 and a protrusion piece 72 retained by the backing piece 70. The second button member 68 includes a dome piece 74 and a capture piece 76 retained by the dome piece 74. The backing piece 70 and the protrusion piece 72 are attached together via crimping or the like. One exemplary crimping process is described in U.S. Pat. No. 6,247,209 to YKK Universal Fasteners, Inc. The dome piece 74 and the capture piece 76 are similarly attached together via crimping or the like.

[0046] The protrusion piece 72 has a first protrusion and a second protrusion, which may take the form of a first sharp prong 80 and a second sharp prong 82. Each of the sharp prongs 80, 82 has a tip 83 with a generally pointed shape. The strap 32 has a first opening 84 and a second opening 86. The first and second openings 84, 86 may be easily formed by the first and second sharp prongs 80, 82 during the process of attaching the first and second button members 66, 68 together. Thus, the first and second sharp prongs 80, 82 have the structural strength and sharpness to pierce the strap 32. In this application, “piercing” refers to a process by which one member is actuated to form a hole in a second member.

[0047] The capture piece 76 has an annular trough 88 positioned such that the first and second sharp prongs 80, 82 are able to simultaneously impinge against the annular trough 88 when the first and second button members 66, 68 are urged together. The annular trough 88 may also be pierced by the first and second sharp prongs 80, 82. The manner in which the first and second button members 66, 68 are attached together will be shown and described in greater detail in connection with FIG. 3, as follows.

[0048] Referring to FIG. 3, a side elevation, section view illustrates the button 56 in a fully assembled state, with the first and second button members 66, 68 attached together on either side of the intermediate portion 36 of the strap 32. As shown, the backing piece 70 has an outer wall 90 against which the protrusion piece 72 rests. The outer wall 90 has an interior surface 92 with a generally circular shape. The backing piece 70 also has a retaining lip 94, which operates to retain the protrusion piece 72. The retaining lip 94 may initially extend from the outer wall 90 along the transverse direction 64, and may be deflected to assume the configuration of FIG. 3 via crimping or some other process.

[0049] The retaining lip 94 defines an aperture 95 of the backing piece 70, through which a portion of the protrusion piece 72 is partially exposed. The protrusion piece 72 has a disc 96 from which the first and second sharp prongs 80, 82 extend nearly perpendicularly. The disc 96 has a periphery 97 that is sandwiched between the retaining lip 94 and the interior surface 92.

[0050] The dome piece 74 has a domed outer wall 98, which cooperates with the capture piece 76 to define an enclosure, in the form of a domed chamber 99. The domed outer wall has a domed interior surface 100 that contacts the tips 83 of the sharp prongs 80, 82 to induce the desired plastic deflection. In this application, an “enclosure” need not be fully enclosed from all sides, but simply has an interior region and features capable of interlocking with a member to retain the member within the interior region.

[0051] The dome piece 74 also has a retaining lip 102 shaped to retain the capture piece 76. Like the retaining lip 94 of the backing piece 70, the retaining lip 102 may initially extend generally along the transverse direction 64 from the domed outer wall 98, and may be deformed into the configuration illustrated in FIG. 3 via crimping or the like. The retaining lip 94 defines an aperture 103 through which a portion of the capture piece 76 is exposed. The capture piece 76 has a curled edge 104 that lies directly inward of the retaining lip 94 to facilitate secure retention of the capture piece 76 by the capture piece 76.

[0052] The first and second button members 66, 68 may relatively easily be attached together to provide the button 56. According to one exemplary method, the first and second button members 66, 68 are first aligned with each other and oriented as shown in FIG. 2. The first side 38 of the strap 32 faces the first button member 66 and the second side 39 of the strap 32 faces the second button member 68. The aperture 95 and the aperture 103 are oriented to face each other. The alignment process may be performed with a specialized machine (not shown) designed to load the first and second button members 66, 68 from a hopper into dies or other fixtures.

[0053] The first and second button members 66, 68 are then urged toward each other in the transverse direction 64 such that the sharp prongs 80, 82 pierce the intermediate portion 36 of the strap 32 to form the first and second openings 84, 86. The first and second button member 66, 68 may be electrically, pneumatically, or hydraulically driven by the machine. The sharp prongs 80, 82 then pierce the annular trough 88 of the capture piece 76 to form a first opening 105 and a second opening 106 in the annular trough 88. The sharp prongs 80, 82 continue to move in the transverse direction 64 until the tips 83 contact the domed interior surface 100.

[0054] When the tips 83 contact the domed interior surface 100, the curvature of the domed interior surface 100 forces the tips 83 to move generally inward to permit continued transverse motion of the protrusion piece 72 with respect to the second button member 68. The tips 83 move toward each other and toward the axis of the button 56, causing the first and second sharp prongs 80, 82 to bend. The die or other fixture that holds the second button member 68 may be shaped to reinforce the domed outer wall 98 to ensure that significant deflection of the domed outer wall 98 does not occur during the button installation process.

[0055] Due to the moments exerted on the sharp prongs 80, 82, the bend in each of the sharp prongs 80, 82 may be sharp enough to constitute a fold similar to that of a staple. The tips 83 slide past each other so that the end portions of the sharp prongs 80, 82 lie generally alongside one another, as illustrated in FIG. 3.

[0056] The bending motion of the sharp prongs 80, 82 is sufficient to constitute plastic deflection of the sharp prongs 80, 82. Hence, the sharp prongs 80, 82 do not tend to relax back into straight configurations, but rather remain in their folded state. In the folded state, a central portion 108 of the capture piece 76 interferes with withdrawal of the sharp prongs 80, 82 from the domed chamber 99.

[0057] Thus, first and second button members 66, 68 will not tend to “snap” apart when the first and second button members 66, 68 are pulled apart by a threshold displacement, as would probably be the case with most snap-fit web stop button arrangements. The attachment of the first and second button members 66, 68 is therefore relatively stable and reliable.

[0058] After assembly, the outer surfaces of the outer wall 90 and the domed outer wall 98 remain visible to the user. If desired, these outer surfaces may be painted or plated to match the color of the strap 32 and/or that of the interior trim of the vehicle. It may be desirable, in certain instances, to provide a somewhat larger button with easier color control. Such an embodiment will be shown and described with reference to FIG. 4, as follows.

[0059] Referring to FIG. 4, a side elevation, section view illustrates a web stop button, or button 156, according to another embodiment of the invention. The button 156 may be used with the remaining components of the seat belt 10 and in place of the button 56. Hence, the button 156 is shown attached to the intermediate portion 36 of the strap 32.

[0060] The button 156 has a first button member 166 and a second button member 168 that are configured in a manner somewhat similar to the first and second button members 66, 68 of the previous embodiment. The first and second button members 166, 168 are constructed substantially of a metal such as brass. In the alternative, other materials may be used, as mentioned in connection with the previous embodiment.

[0061] The first button member 166 has a backing piece 170 slightly different from the backing piece 70, and a protrusion piece 72 substantially identical to that of the previous embodiment. Similarly, the second button member 168 has a dome piece 174 slightly different from the dome piece 74, and a capture piece substantially identical to that of the previous embodiment.

[0062] The protrusion piece 72 has first and second protrusions, which may be configured as first and second sharp prongs 80, 82, each of which has a tip 83 with a generally pointed shape. The first and second sharp prongs 80, 82 are capable of piercing the strap 32 to form first and second openings 84, 86 in the intermediate portion 36. The first and second sharp prongs 80, 82 are also capable of piercing an annular trough 88 of the capture piece 76 of the second button member 168.

[0063] As shown, the backing piece 170 has an outer wall 190 somewhat smaller than that of the previous embodiment. The outer wall 190 has an interior surface 192 against which the protrusion piece 72 rests. A retaining lip 194 retains the protrusion piece 72 and defines an aperture 195 through which a portion of the protrusion piece 72 is exposed. The protrusion piece 72 has a disc 96 with a periphery 97 gripped between the retaining lip 194 and the interior surface 192.

[0064] The dome piece 174 has a domed outer wall 198 that cooperates with the capture piece 76 to define an enclosure in the form of a domed chamber 199. The domed outer wall 198 has a domed interior surface 200, and is slightly different in shape from the domed outer wall 98 of the previous embodiment. The dome piece 174 also has a retaining lip 202 that retains the capture piece 76. The retaining lip 202 defines an aperture 203 through which a portion of the capture piece 76 is exposed. The retaining lip 202 curves around a curled edge 104 of the capture piece 76 to grip the curled edge 104.

[0065] Attachment of the first and second button members 166, 168 to each other is performed in a manner similar to that described above, in connection with the previous embodiment. The first and second sharp prongs 80, 82 pierce the annular trough 88 to form first and second openings 105, 106 in the annular trough 88. The sharp prongs 80, 82 contact the domed interior surface 200 and are deflected thereby to reach the generally folded state illustrated in FIG. 4. A central portion 108 of the capture piece 76 then interferes with withdrawal of the sharp prongs 80, 82 from the domed chamber 199.

[0066] A first plastic cap 210 is disposed to cover the first button member 166 and a second plastic cap 212 is disposed to cover the second button member 168. The first plastic cap 210 has a receiving chamber 214 shaped to receive the backing piece 170. The first plastic cap 210 also has a retaining lip 216 shaped to abut the retaining lip 194 of the backing piece 170 to keep the backing piece 170 within the receiving chamber 214.

[0067] The retaining lip 216 may initially extend generally along the transverse direction 64, and may be heat staked into the configuration illustrated in FIG. 4 after positioning of the backing piece 170 within the receiving chamber 214. Alternatively, the retaining lip 216 may be crimped, insert molded, or otherwise shaped in the desired manner. U.S. Pat. No. 5,134,756 provides one exemplary method of attaching a plastic cap to a metal button structure.

[0068] The retaining lip 216 defines an aperture 218 through which the sharp prongs 80, 82 extend. The first plastic cap 210 also has a peripheral lip 220 that extends toward the first side 38. The peripheral lip 220 may contact the first side 38, or may simply terminate close to it, as shown in FIG. 4. The first plastic cap 210 has a central indentation, which may be used to identify the first plastic cap, display a trademark, or the like.

[0069] The second plastic cap 212 has a receiving chamber 224 within which the second button member 168 is disposed. The second plastic cap 212 also has a retaining lip 226 that abuts the retaining lip 202 of the dome piece 174 to keep the dome piece 174, and thence, the entire second button member 168, within the receiving chamber 224. As with the retaining lip 216 of the first plastic cap 210, the retaining lip 226 may initially extend generally in the transverse direction 64. The retaining lip 216 may be heat staked, crimped, insert molded, or otherwise processed to provide the shape illustrated in FIG. 4 after insertion of the second button member 168 into the receiving chamber 224.

[0070] The retaining lip 226 defines an aperture 228 through which the sharp prongs 80, 82 are inserted to reach the second button member 168. The second plastic cap 212 also has a peripheral lip that extends toward the second side 39, in general alignment with the peripheral lip 220 of the first plastic cap 210. The peripheral lip 230 may contact the second side 39, or may simply terminate close to it, as shown in FIG. 4.

[0071] The first and second plastic caps 210, 212 enlarge the effective size of the button 156. The first and second button members 166, 168 may, alone, be approximately one-quarter inch in diameter. The first and second plastic caps 210, 212 may each be about one-half inch in diameter.

[0072] Additionally, first and second plastic caps 210, 212 provide for relatively easy color matching because the same plastic used to form the interior trim of the vehicle may be molded or otherwise processed to form the plastic caps 210, 212. In alternative embodiments of the invention, only one of the caps 210 or 212 may be present, and one of the button members 166, 168 may remain uncovered. According to other alternatives, caps for web stop buttons need not be made from plastic, but may be constructed of other materials including metals, ceramics, elastomers, and composite materials.

[0073] The invention encompasses a variety of first and second button member configurations. Those of skill in the art will recognize that many characteristics of the embodiments described above could be varied, beyond the variations explicitly described above, within the scope of the invention. FIG. 5 illustrates one exemplary alternative embodiment in which some of these variations are present.

[0074] Referring to FIG. 5, a side elevation, section view illustrates a web stop button, or button 256, according to another alternative embodiment of the invention. The button 256 may be used in place of the button 56 in the seat belt 10 of FIG. 1; hence, the button 256 is shown attached to the intermediate portion 36 of the strap 32.

[0075] As illustrated, the button 265 has a first button member 266 and a second button member 268. In contrast with the previous embodiments, each of the first and second button members 266, 268 is a substantially unitary, single piece. The first and second button members 266, 268 are constructed of a metal such as copper. As with the previous embodiments, different materials may alternatively be used to form the button members 266, 268.

[0076] The first button member 266 has first, second, and third protrusions, which may take the form of a first sharp prong 280, a second sharp prong 282, and a third sharp prong (not visible in the section view of FIG. 5). The first sharp prong 280, the second sharp prong 282, and the third sharp prong are distributed about an axis of symmetry of the button 256 in radially symmetrical fashion. Hence, the section plane intersects the first sharp prong 280, but not the second sharp prong 282 or the third sharp prong. Each of the sharp prongs 280, 282 has a tip 83 with a pointed shape.

[0077] The first and second prongs 280, 282 are strong and sharp enough to pierce the strap 32 to form first and second openings 284, 286 in the strap 32. The third sharp prong is similarly shaped to provide a third opening (not shown) in the strap 32. The first button member 266 has an outer wall 290 with a generally disc-like shape. A contact lip 294 extends inward from the periphery of the outer wall 290 to contact the first side 38 of the intermediate portion 36.

[0078] The second button member 268 has a domed outer wall 298 that defines an enclosure in the form of a domed chamber 299. The domed outer wall 298 does not possess a conventional concave shape, like those of the previous embodiments. Rather, the domed outer wall 298 has an arcuate cross section that has been revolved about the axis of symmetry of the button 256 to provide a shape resembling a portion of a torus. In this application, “domed” refers to a shape, at least a portion of which has an arcuate or arc-like cross section. The domed outer wall 298 has a domed interior surface 300 positioned to contact and deflect the first and second sharp prongs 280, 282 and the third sharp prong.

[0079] The second button member 268 also has a contact lip 302 that extends toward the second side 39 to contact the second side 39. The second button member 268 further has an aperture 303 through which the first and second sharp prongs 280, 282 and the third sharp prong are able to enter the domed chamber 299 without piercing the second button member 268.

[0080] Attachment of the first and second button members 266, 268 to each other to form the button 256 is similar to that of the previous embodiments. The first and second button members 266, 268 are first aligned on opposite sides of the intermediate portion 36 and oriented such that the first and second sharp prongs 280, 282 and the third sharp prong face the aperture 303 of the second button member 268.

[0081] The first and second button members 266, 268 are then urged toward each other and the first and second sharp prongs 280, 282 and the third sharp prong pierce the intermediate portion 36 to form the first and second openings 284, 286 and the third opening in the intermediate portion 36 of the strap 32. The first and second sharp prongs 280, 282 and the third sharp prong then pass into the domed chamber 299 via the aperture 303 without piercing the second button member 268.

[0082] The tips 83 of the first and second sharp prongs 280, 282 and the third sharp prong contact the domed interior surface 300 and are plastically deflected outward by the curvature of the domed interior surface 300. Thus, the first and second sharp prongs 280, 282 reach the outward-folded positions illustrated in FIG. 5. The third sharp prong is similarly folded. A retention wall 304 extends from the aperture 303 to the contact lip 302 to interfere with withdrawal of the first and second sharp prongs 280, 282 and the third sharp prong from the domed chamber 299. Thus, as with the previous embodiments, plastic deflection provides relatively secure and reliable attachment of the first and second button members 266, 268 to form the button 256.

[0083] Through the use of the web stop apparatus and method of the present invention, web stop buttons may be easily and inexpensively installed. The web stop buttons may have a high reliability and durability, so that the frequency of warranty repairs due to webs stop button failure is drastically decreased. Thus, the cost-effectiveness, dependability, and convenience of seat belts may be increased to enhance automotive safety.

[0084] The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

1. A seat belt for restraining motion of a vehicle occupant, the seat belt comprising: a strap having a first side and a second side; a first button member disposed adjacent to the first side, the first button member comprising a first protrusion extending through the strap; and a second button member disposed adjacent to the second side, the second button member comprising an enclosure shaped to induce plastic deflection of the first protrusion in response to pressure urging the first and second button members together, wherein the plastically deflected first protrusion is shaped to interlock with the enclosure to hold the first and second button members together.
 2. The seat belt assembly of claim 1, wherein the first protrusion comprises a first sharp prong and the enclosure comprises a domed chamber.
 3. The seat belt assembly of claim 2, wherein the first button member further comprises a second sharp prong symmetrically arranged with the first sharp prong about an axis of symmetry of the first button.
 4. The seat belt assembly of claim 3, wherein the first and second sharp prongs are plastically deflected in such a manner that the first and second sharp prongs are folded toward each other to lie generally perpendicular to the axis of symmetry.
 5. The seat belt assembly of claim 1, wherein the first button member comprises a protrusion piece in which the first protrusion is integrally formed, and a backing piece that retains the protrusion piece, and wherein the second button member comprises a capture piece and a dome piece that retains the capture piece to define the enclosure.
 6. The seat belt assembly of claim 1, wherein the first and second button members are constructed substantially of metal.
 7. The seat belt assembly of claim 6, further comprising a plastic cap attached to one of the first and second button members.
 8. A seat belt for restraining motion of a vehicle occupant, the seat belt comprising: a strap having a first side and a second side; a latch plate shaped to slidably capture the strap; and a web stop button attached to the strap to restrict motion of the latch plate along the strap, the web stop button comprising a first button member disposed adjacent to the first side and a second button member disposed adjacent to the second side, wherein the first button member is shaped such that a portion of the first button member deflects plastically to interlock with the second button member in response to pressure urging the first and second button members together.
 9. The seat belt of claim 8, wherein the first button member comprises a first protrusion and the second button member comprises an enclosure, wherein the first protrusion plastically deflects to interlock with the enclosure in response to pressure urging the first and second button members together.
 10. The seat belt of claim 9, wherein the first protrusion comprises a sharp prong and the enclosure comprises a domed chamber having a domed interior surface shaped to contact and deflect the first protrusion in response to pressure urging the first and second button members together.
 11. The seat belt of claim 10, wherein the domed chamber is disposed to be pierced by the sharp prong in response to pressure urging the first and second button members together.
 12. The seat belt of claim 10, wherein the first button member further comprises a second sharp prong symmetrically arranged with the first sharp prong about an axis of symmetry of the first button.
 13. The seat belt of claim 12, wherein the first and second sharp prongs plastically deflect by folding generally toward each other to lie nearly perpendicular to the axis of symmetry.
 14. The seat belt of claim 9, wherein the first button member comprises a protrusion piece in which the first protrusion is integrally formed, and a backing piece that retains the protrusion piece, and wherein the second button member comprises a capture piece and a dome piece that retains the capture piece to define the enclosure.
 15. The seat belt of claim 8, wherein the first and second button members are constructed substantially of metal.
 16. The seat belt of claim 15, wherein the first and second button members are constructed substantially of brass.
 17. The seat belt assembly of claim 15, further comprising a plastic cap attached to one of the first and second button members.
 18. The seat belt assembly of claim 17, wherein the plastic cap comprises a first button cap attached to the first button member, the seat belt assembly further comprising a second button cap made of plastic and attached to the second button member.
 19. The seat belt assembly of claim 8, wherein the strap comprises a first end, a second end, and an intermediate portion between the first and second ends, wherein the intermediate portion is slidably captured by the latch plate, the seat belt assembly further comprising a retractor attachable to the first end and the vehicle to take up the first end, an anchor attachable to the second end and the vehicle to anchor the second end to the vehicle, and a buckle attachable to the vehicle to removably retain the latch plate.
 20. A seat belt for restraining motion of a vehicle occupant, the seat belt comprising: a strap having a first side and a second side; a first button member disposed adjacent to the first side, the first button member comprising a first protrusion extending through the strap; and a second button member disposed adjacent to the second side, the second button member comprising an enclosure pierced by the first protrusion in response to pressure urging the first and second button members together such that the first protrusion and the enclosure are interlocked to hold the first and second button members together.
 21. The seat belt of claim 20, wherein the first protrusion comprises a sharp prong and the enclosure comprises a domed chamber having a domed interior surface shaped to contact and deflect the first protrusion in response to pressure urging the first and second button members together.
 22. The seat belt of claim 21, wherein the first button member further comprises a second sharp prong symmetrically arranged with the first sharp prong about an axis of symmetry of the first button.
 23. The seat belt of claim 22, wherein the first and second sharp prongs plastically deflect by folding generally toward each other to lie nearly perpendicular to the axis of symmetry.
 24. The seat belt of claim 20, wherein the first button member comprises a protrusion piece in which the first protrusion is integrally formed, and a backing piece that retains the protrusion piece, and wherein the second button member comprises a capture piece and a dome piece that retains the capture piece to define the enclosure.
 25. The seat belt of claim 20, wherein the first and second button members are constructed substantially of metal.
 26. The seat belt assembly of claim 25, further comprising a plastic cap attached to one of the first and second button members.
 27. A method for manufacturing a seat belt for restraining motion of a vehicle occupant, the seat belt comprising a strap having a first side and a second side, a first button member comprising a first protrusion, and a second button member comprising an enclosure, the method comprising: forming an opening in the strap; disposing the first button member adjacent to the first side such that the first protrusion extends through the opening; disposing the second button member adjacent to the second side; and pressing the first and second button members together such that the first protrusion enters the enclosure and is plastically deflected to interlock with the enclosure to hold the first and second button members together.
 28. The method of claim 27, wherein forming the opening in the strap comprises piercing the strap pressing the first protrusion into the first side of the strap.
 29. The method of claim 27, wherein the first protrusion comprises a sharp prong and the enclosure comprises a domed chamber having a domed interior surface, wherein plastically deflecting the first protrusion comprises urging a tip of the sharp prong against the domed interior surface.
 30. The method of claim 29, wherein the first button member further comprises a second sharp prong symmetrically arranged with the first sharp prong about an axis of symmetry of the first button, wherein the first and second button members are pressed together such that the second sharp prong enters the enclosure and is plastically deflected to interlock with the enclosure, wherein the first and second sharp prongs are plastically deflected to lie generally alongside each other.
 31. The method of claim 29, wherein pressing the first and second button members together such that the first protrusion enters the enclosure comprises piercing the enclosure with the first protrusion.
 32. The method of claim 27, wherein the first and second button members are constructed substantially of metal, wherein the seat belt further comprises a plastic cap, the method further comprising attaching the plastic cap to one of the first and second button members.
 33. A method for manufacturing a seat belt for restraining motion of a vehicle occupant, the seat belt comprising a strap having a first side and a second side, a first button member comprising a first sharp prong and a second sharp prong, and a second button member, the method comprising: aligning an axis of the first button member with an axis of the second button member; pressing the first and second sharp prong into the first side to form first and second openings by piercing the strap, wherein the sharp prongs are formed substantially of a metal; and pressing the first and second button members together to induce the first and second button members to interlock with each other, thereby holding the first and second button members together.
 34. The method of claim 33, wherein the second button member comprises a domed chamber having a domed interior surface, wherein inducing the first and second button members to interlock with each other comprises urging tips of the first and second sharp prongs against the domed interior surface to plastically deflect the first and second sharp prongs, thereby causing the first and second sharp prongs to interlock with the domed chamber.
 35. The method of claim 34, wherein the first button member comprises a backing member constructed substantially of metal and the second button member comprises a dome member constructed substantially of metal, the method further comprising attaching a plastic cap to one of the backing member and the dome member. 